US Secretary of State John Kerry (r.) talks to the media about negotiations over Iran's nuclear program, as Libya Prime Minister Ali Zeidan (c.) and British Foreign Secretary William Hague look on Sunday.

WASHINGTON — Iran’s acceptance this week of a deal to freeze much of its nuclear program for at least six months is placing a new spotlight on economic sanctions as a tool for getting outlier nations to “yes” on stopping activities the international community finds objectionable.

The unprecedented sanctions that the US and other international players, in particular the European Union (EU), placed on Iran’s economy in recent years played a key role in bringing Iran to the negotiating table, international affairs analysts widely agree.

But Iran’s situation may have been almost tailor-made for sanctions to produce results, some experts say. A large middle-class population had just this year brought to power a new president with a mandate to relieve Iranians’ economic pain, they note, and to fashion a new, less combative relationship between Iran and the wider world – including arch-enemy America.

That combination of widespread public demands for sanctions relief and a change in Iran’s political order – from the fiery and sanctions-mocking (publicly, at least) President Mahmoud Ahmadinejad to the more temperate and internationalist President Hassan Rouhani – played a key role in bringing Iran to the table.

“There’s no question that the sanctions have had an impact on [Iran’s nuclear] program, and that they helped bring the new government to power,” says William Luers, director of the Iran Project at the Carnegie Endowment for International Peace in Washington. “But [the Iranians] want more than money and access [to markets], they are looking for a change in their relations with the region.”

Yet, as important as the arrival of Rouhani may have been, it was equally important that Iran was facing international powers – including, critically, the US – that were ready to give priority to diplomacy and to begin rewarding Iran in exchange for specific actions, other experts say.

“Yes, the sanctions were critical, but the possibility of reciprocal action was also important,” says George Lopez, an international economic sanctions expert in Washington.

The prospect of real incentives brought Iran to the table, he adds, and now that a short-term deal is in hand, the next phase – the six months of negotiations aimed at reaching a comprehensive deal – should be about “astute rewards for other concessions.”

That means now is not the time to pile on new sanctions, as some in Congress are demanding, he says. “There’s the thought out there that once your foot is on the other guy’s neck you ought to stomp on it once or twice to make sure he gets the message,” says Dr. Lopez, who is vice president of the US Institute of Peace’s Academy for International Conflict Management and Peacebuilding in Washington. “But it’s more likely to be counterproductive.”

On Tuesday, Secretary of State John Kerry sent a video to members of Congress in which he argues for a pause in any new sanctions legislation. Kerry says that “everybody knows” that sanctions will be reinforced if Iran violates the terms of the interim deal, but he insists that new sanctions now could throw off the best chance of stopping Iran from obtaining a nuclear weapon through diplomacy.

Lopez, who has worked with the United Nations on sanctions implementation related to North Korea, says that sanctions aimed at nuclear nonproliferation are different from other kinds of sanctions – those addressing human rights violations, for example – because they target a specific program that has physical parts and materials that can be forbidden.

“You can be product-focused and concentrate on certain kinds of trade,” Lopez says.

Another critical factor in the “success” of Iran sanctions was what Lopez calls a “multileveling,” under which United Nations sanctions focused on the nuclear program, while the US and EU went further with targeted sanctions on Iran’s currency and oil revenues.

It was those latter sanctions that hit Iran’s economy with intensifying force – and which helped build public pressure for a new direction with the outside world.

But Lopez notes that the US had to be wary of “bad PR” from indiscriminate application of economic sanctions. US officials no doubt had in the back of their mind the nightmare the US faced from reports of the “baby-killing” sanctions the US imposed on Iraq under Saddam Hussein.

Another point is that the “multileveling” of sanctions that Iran has been subject to would not work everywhere. In the case of North Korea, the absence of a middle-class population used to a comfortable standard of living and to consuming imported products made targeted economic sanctions unrealistic and ineffective.

Nor does the North Korean dictatorship permit a politically franchised and engaged population that would be able to express its will at the ballot box.

“With North Korea you’ve got to hurt the elites, even as you continue to contain the materials that feed their program,” he says. “It’s a very different approach.”

In the Iran case, the challenge now for world powers will be to demonstrate – to Iranians and to the world -- that the sanctions were not an end, but a means.

“The interesting question is, can we take the sanctions that created these negotiations [and] now use them to put in concrete … the best possible arrangement" for permanently and verifiably stopping Iran short of obtaining a nuclear weapon, says Thomas Pickering, a retired career ambassador who works with the Iran Project, a bipartisan group of former US officials seeking improved engagement between the US and Iranian governments.

The US and world powers should now focus on using the sanctions “creatively,” he says, “to achieve a limitation of the [Iranian] program.”